This invention relates generally to pyrometallurgy, and specifically to a method for sealing holes or channels drilled in cooling blocks used in pyrometallurgical furnaces
In the pyrometallurgy of copper, as well as many other metals, furnaces of various designs are used for a number of processes including smelting ore and or concentrates, converting matte and fire-refining metal. In many cases, these furnaces are equipped with cooling blocks. Cooling blocks are used to moderate the furnace temperature to achieve various ends, such as prolonging refractory life or assisting in the introduction or removal of various materials from the furnace.
Cooling blocks are constructed typically of cast copper. These blocks often contain internal channels or conduits through which a cooling medium can be circulated to assist in regulating the temperature of the furnace. These channels within the cooling blocks are formed generally either during the casting procedure or through a drilling operation. Combining these two procedures is also common, such that some of the channels are formed by casting and other channels, typically the channels interconnecting the cast channels, are formed by drilling. For example, a cooling block might be cast with a number of horizontal channels extending into the cooling block and running parallel to one another. Vertical channels can then be drilled perpendicular to these horizontal channels to interconnect and establish fluid communication between the channels. In another example, intersecting horizontal and vertical holes are drilled completely through the block and once interconnected, the open ends of the channels are plugged or sealed.
Regardless of the method by which the channels are formed, typically at least one plug is necessary to seal unwanted entry holes into the cooling block such that the flow integrity of the internal cooling channels is maintained. Failure to properly plug these entry holes can result in leakage of the cooling fluid. In the past, mechanical plugs have been used to seal these holes. Typically a metal plug is inserted into an undesired hole so that the top of the plug is flush with the external surface of the cooling block. Once positioned within the hole, the plug is then welded into place to serve as a seal against cooling fluid leakage.
There are several disadvantages in the process of plugging holes in the above-described manner. First, welding is undesirable because surface contaminants can result in a lack of bonding and lead to gas porosity. Because the coolant circulating within the channels may be under pressure, a poor bond or a porous weld yielding a weak joint can result in a blowout of the plug. Additionally, these types of welds result in a bead such that the surface of the cooling block does not have a smooth finish. However, machining the weld bead to produce a smooth surface is undesirable because this would weaken the integrity of the weld.
Another disadvantage with the plugging process of the prior art is that the junction of the plug and the cooling block forms a seam. Seams are undesirable because they typically result in leaks, especially when the sealed plug in question is under pressure.
Welds such as those described above are also commonly used to secure pipe fittings and the like to cooling blocks. Typically, a fitting is threaded to be received by the correspondingly threaded internal diameter of a channel. However, these threads alone generally do not provide the sufficient mechanical strength to secure such fittings. Therefore, additional means are often necessary for securing the fitting within the channel. In the past, a simple weld at the joint between the fitting and the cooling block has been utilized. However, welds such as these are also subject to the problems described above. Additionally, these types of welds can damage the integrity of the fitting, causing leaks in the fitting at the point of the weld.
One known method of repairing holes or weak points that do develop in such fittings, either at their point of attachment to a cooling block or elsewhere along the perimeter of the fittings, is to secure a jacket over the damaged portion of the fittings. These jackets are typically secured by welding or other mechanical means such as clamping. However, this method of addressing damaged fittings is undesirable because the damaged areas are not repaired but only temporarily mended. Specifically, the ruptured (or weak) area is not sealed (or reinforced) in any way, but only covered such that this method is only temporary in nature. As a result, over time leaking fluid tends to migrate along the outer surface of the fittings, underneath the jacket, until leaks appear along the joint between the jacket and the fitting.
As is evident from the preceding discussion, a need exists for an economical and inexpensive process which can provide a seamless seal for plugging holes in cooling blocks. The process should yield a plug which is less pressure sensitive than the process of the prior art. Moreover, desirably this process should also be useful for securing pipe fittings and the like to such cooling blocks to provide a strong mechanical bond without damaging the fittings. Still, further, the process should be able to repair ruptured or weakened areas in fittings.